Hydraulic motors and other units having a rotary output are frequently used with devices for which information as to the positioning and/or speed and/or direction of rotation is useful. Examples include robotic arms, salt spreading units, scissor lifts, winches and power steering units. Some units utilize sensors deep within the housing of the units together with specialized shafts. The Parker hydraulic motor with its slotted shaft and inductive sensor is an example. Other units utilize sensors in specially machined intermediate members between a device and its associated motor. The White Hydraulics motor with cast cap having a screwed in separate sensor is an example. In this motor (FIG. 11) a screw-in sensor 90 is provided with access to, and adjustment of, the clearance 92 through an enlarged dust cap 93 in original and subsequent installations. Typically it is necessary to have a separated power unit to do this. Additional units use specialized housings with multiple sensors. The Ross gear commutation apparatus disclosed in U.S. Pat. No. 4,767,292, Electrical Commutation Apparatus, is such a unit.
These units necessitate complicated housings, additional individual manufactured parts and/or additional components. These add to the complexity of the overall device, increasing manufacturing maintenance and other costs relative to the hydraulic units. The units typically require specialized integral design and/or relatively significant individual adjustments. The units also typically have to be removed and rebuilt if there are sensor problems. The units are thus costly to both build and maintain.